Vulcanizing rubber



GEQRQE H. STEt E'BlS, 01? NEWARK, NEW JERSEY.

VULCANIZING RUBBER.

No Brewing. original application. filed June 25, 1923, filed January 26, 1925.

To all whom it mac; concern:

Be it lmown that I, Grouse H. STEVENS, a, citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in Vulcanijzing Rubber, oi which the following is a specification. j

This invention relates to improvements in the use of organic nitrogenous substances that assist in or accelerate the vulcanization oi rubber, end has for its object the utilization of new products that are mentioned for this purpose,

The use of organic nitrogenous compounds in the vulcanization of rubber is quite genoral and the products so used are technically termed accelerators. f

il/ liether such bodies set at catalysts, sulphur carriers, polymerizers, activators, or accelerators, is not the purpose of this speciiication to discuss, but I make use or the conventional term accelerator in my mention of them.

In experimental work with various nitrogenous organic compounds that I have used, to assist in the vulcanization of rubber, I have found that certain derivatives of carbodiimides form exceedingly valuable products for this purpose, and contrary to the general impression that they are not suitable use in rubber vulcanization.

In a previous patent application N0v 399,97 1 have mentioned. tetraphenylmel ,a-mine (tetraphenyltricarbodiimide) e phenylated carbc- --diimide as an eccelorator, and I have also found that other derivatives of carbodiimides are also very efficient aids to vulcanization, and especially where they are markedly basic in character.

An example of such a product'is tetratolylmelamine, (tetratolyltricarhodiimide expressed by the following formula:

i to s e tie oi This product has a nitrogen content of over 17% and is comparatively stable, during the period, and at the usual temperatures of vulcanization.

The product can be produced in various ways, but one manner is to unite two mole- Serial No. 6%,765. Divided and this application Serial No. 955.

rivative of carbodiimide. i

un Nrif.

A similar produch-results from the corre fsponding union of t 0 molecules of carboxylilimide (C H of carbodixylilimide ro u uzoeio iie which then would be tetraxyliltricarbodiimide.

CBGHSSNG I 3 2 (G8HD)4N6 This body also proves a good accelerator but with a somewhat lower nitrogen con,- tent.

One method of'obtaining carbo- (mono or di substituted) -imides, is by dcsulphurizing the corresponding subst tuted thioureas. Such desulphurizing is however subject to many modifications, depending on the presence of other products and. so mixed products may result.

E or instance-mustard oil is frequently present in disubstituted thiourea. If desulphurizetion of disubstituted thiourea takes place then in the presence of ammonia and mustard oil, :1 formation of the correspending monosubstituted thiourea could take place, and e 'desulphurization of both thioureas would then yield the two corresponding carhosubstituted -imides.

-These carbo- -imides then might be c0mhined to tetresubstituted -tricarbodiimide, even though intermediate products form during such combination. There are also several other methods available for the production of these products.

Tctratolyltricarbodiimide seems to be of such st-iible character that it can be used even in a very impure state and still give excellent results. It is cryptoc'ryst alline and so its isolation in a regular crystalline with one molecule vused, either in its amorphus, or gummy state, or in mixed isomeric torm, or with its related by-products and impurities present, without materially diminishing its usefulness.

Merely its degree o1 purity should be determined and then formulae for its use would be based on such pure content.

This accelerator proves itself of unusualvalue in tire and tube compounds.

An example of a representative rubber compound and its cure, using tetratolyltricarbodiimide as an accelerator would be:

'For high tensile blank.

82 Smoked sheets. 5 Zinc oxide.

7 Barytes. 5%70 Sulphur. O Tetratolyltricarbodiimide.

Cure:

44 minutes at 40 lbs. steam pressure, or: 20 minutes at 40 lbs. steam pressure for best aging.

An unusually high tensile results from the first of these cures.

For friction 815007;.

82 Smoked sheets.

5 Sulphur. 2 Magnesium oxide. 1O Zinc oxide.

0 Tetratolyltricarbodiimide.

ure: 35 minutes at 37 lbs. steam pressure.

I 01' red tube stock.

69 76 Smoked sheets.

18 Golden or crimson antimony.

5 Zinc oxide.

7 Barytes.

0%% Tetratolyltricarbodiimide.

Many of the derivatives of carbodiimides are or ptocrystalline compounds with the amorp ous appearance more frequently in evidence than the crystalline form, and so they are not readily separated from their accompanying compounds, that may be present due to their origin, or present byproducts of their formation.

Carbodiixnide as well as the phenyl, tolyl, and xy'lil substitution products thereof may some of them assume the form of polymeric modifications.

The use of the term cryptocrystalline in this specification is intended to designate a body that is at times amorphous, either in fact orj ILZLDPQMHDCG, and yet at other times is of a definite crystalline form. Hidden crystals would be a concise drfinition.

These cryptocrystalline carbodiimide de rivatives seem to be generally of great eagues bility at t ie temperatures required for vul- Another characteristic of them is, that frequently they are higher in ltinp bodies, resulting from the decomposition of lower melting bodies, which in acceleration means, the original accelerator oli lower melting point is progressively"decomposed under vulcanization into the higher melting accelerator, and in theory, eventually the lower melting accelerator becomes more or less exhausted and when the cure is completed, the higher melting accelerating material then present, inhibits the activity of further vulcanization in the cold, or expressed in technical parlance, the resulting rubber product thus has, better aging qualities}? or stands aging better.

ray invention then consists in utilizing, in rubber vulcanization, the bodies herein mentioned and Whichappear to have superior qualities to many of the compounding ingredients used heretofore in compounding and vulcanizing rubber.

While I have described In invention in detail, and. stated the manner in which the products mentioned may be prepared and used, it is to be understood that l do not mean to be limited in this specification to the use of the particular ingredients mentioned examples, or in any Way, except by the claims as set forth and annexed herewith.

it is further to be understood that my invention. is not to be construed as dependent on the accuracy or soundness of any of the theories herein expressed, or on the correctness of the structural formulas used to designate the products.

Having now described my invention and having shown in What manner the same may be utilized, what I claim as new, and desire to secure by Letters Patent is:

1. A process of vulcanizi'ng rubber which consists in, inctn'porating a vulcanizing agent with compounded rubber, then under heat, causing the formation of tetraphenyltricarbodiin'iide within the rubber mixture While el'lecting vulcanization;

2. In the vulcanization of rubber the combinati on of: sulphur or a suitable compound of sulphur as a vulcanizing agent; tetraphenyltricarbodiiniide either by itself or in combination with other bodis,as an aid to vulcanization; raw or compounded rubber.-as the product to be vulcanized; and means applied to these united, to client vulcanization.

3. A process ot vulcaniziug rubber which consists in, incorporating into rubber an ac celerator resulting from a combination of desulphurized monoand diphenylthiourea,

then heating lhc resultant. rubber mixture materials when 1 with a vul'canizing agent to effect vulcani zation.

4:. A process oi vulcanizing rubber which consists in, incorporating into rubber anaceelerator resulting from a dipbenylthiourea that has been ,desulphurized in the presence of phenyl mustard oil and ammonia, then heating the resultant rubber mixture with a vulcanizing agent to client vulcanization.

5. Aprocess of vulcanizing rubber Which consists in, incorporating into rubber an accelerator resulting from a combination of carbodiphenylimide and carbomonophenyl-- imide, or of their polymeric modifications respectively, then heating the resultant rubber mixture with a vulcanizing agent to effect vulcanization. a

6. A Vulcanized compound, containing agent, and a combination of desulphurized monoand diphenylthiourea;

8. A vulcanized compound, containing rubber or similar material, a vulcanizing agent, and a diphenylthiourea that has been desulphurized in the presence of phenyl mus tard oil and ammonia.

9. A vulcanized compound, containing rubber or similar material, a vulcanizing agent, and a combination of carbomono-. and carbodiphenylimide, .or of their polymeric modificatlons respectively.

i GEORGE 1. STEVENS. 

